Summaries for Patients|5 December 2006

The summary below is from the full report titled “Interval versus Continuous High-Intensity Exercise in Chronic Obstructive Pulmonary Disease: A Randomized Trial.” It is in the 5 December 2006 issue of Annals of Internal Medicine (volume 145, pages 816-825). The authors are M.A. Puhan, G. Büsching, H.J. Schünemann, E. vanOort, C. Zaugg, and M. Frey.

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What is the problem and what is known about it so far?

Chronic obstructive pulmonary disease (COPD) is a disease of the lungs that is usually caused by smoking. In COPD, lung damage gradually worsens over time. People with COPD are short of breath and sometimes cough and wheeze. Symptoms slowly get worse over time, but most patients also have intermittent bouts of worsening of symptoms. Lung infections, cold weather, and exertion may bring on these bouts. In addition to medications, treatment guidelines recommend high-intensity, continuous exercise to improve lung function. However, this type of exercise can be difficult for people with COPD to tolerate. Some believe that short intervals of exercise may also benefit patients with COPD and may be easier for them to accomplish, but high-quality studies comparing the 2 types of exercise have been unavailable.

Why did the researchers do this particular study?

To find out whether interval exercise produces the same benefits for people with COPD and is easier for them to tolerate than continuous exercise.

Who was studied?

98 patients with COPD in Switzerland.

How was the study done?

The researchers randomly assigned patients to 12 to 15 supervised sessions of either continuous or intermittent high-intensity exercise over 3 weeks followed by unsupervised exercise at home. Patients used exercise cycles during the supervised exercise sessions. Patients assigned to continuous exercise warmed up for 2 minutes, pedaled at high intensity for 20 minutes (or until they needed to stop because of fatigue or other symptoms), and cooled down for 2 minutes. Patients in the intermittent exercise group warmed up for 2 minutes; pedaled for 20 minutes, alternating between 20 seconds at high intensity and 40 seconds at low intensity (or until they needed to stop because of fatigue or other symptoms); and cooled down for 2 minutes. Patients completed a standard questionnaire to evaluate lung function at the start of the study and 5 weeks into the study. This questionnaire is called the Chronic Respiratory Questionnaire or CRQ. Scores on the questionnaire vary from 1 (most severe) to 7 (least severe). The researchers also collected information on the number of times patients had to take unplanned breaks during the supervised exercise sessions.

What did the researchers find?

Both groups experienced similar improvements in CRQ scores. Nearly one half of the patients in the intermittent exercise group could exercise without unintended breaks compared with just less than one quarter of the patients in the continuous exercise group. The average number of breaks was 2 in the intermittent exercise group and 11 in the continuous exercise group.

What were the limitations of the study?

The study looked at patients only during the early weeks of starting a supervised exercise program. The researchers did not study unsupervised exercise or long-term outcomes.

What are the implications of the study?

Patients considering exercise to improve COPD can select either continuous or intermittent exercise.

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